The invention relates in general to vacuum treatment devices and in particular to a new and useful high-vacuum valve, particularly an ultra-high vacuum gate valve, comprising a valve casing with gas inlet and outlet ports and a valve shutter body and an associated drive element.
In vacuum valves, the valve shutter body which, in large valves, is mostly designed as a plate, must be pressed into contact with the valve seat by a sufficiently high pressure to ensure a satisfactory tightness, even to atmospheric pressure, if necessary.
Particular requirements are imposed on ultra-high vacuum valves. Not only an extremely low leakage rate but also a low gas emission and impermeability rate of the sealing element, and heatability up to 400.degree. C., to accelerate the degassing, are required. The two last mentioned requirements can be met only with a metal seal. Then, to obtain low leakage rates, extraordinarily high sealing forces are needed, in the order of magnitude of 100 to 1,000 N per millimeter sealing length. Therefore, very high contact pressures are needed in valves having large diameters and, consequently, a long sealing line along their circumference.
To drive vacuum gate valves, pneumatic actuating mechanism, toggle lever or tapering tracks are used which are disposed between the valve plate and a counterplate. Valve plate and counterplate then bear against the casing along the circumference of the valve ports. To permit absorption of the strong forces by the casing without causing a distortion of the sealing surface, the casing must be extraordinarily stable in shape, which entails high material and manufacturing costs.